Problem - Kevin Tafuro

eset the umask between your adjustment of the umask and any of your file creation
calls, you could potentially create sensitive files with wide-open permissions.
Modifying the umask programmatically is a simple matter of calling the function
umask( ) with the new mask. The return value will be the old umask value. The standard
header file sys/stat.h prototypes the umask( ) function, and it also contains definitions
for a sizable set of macros that map to the various permission bits. Table 2-2
lists the macros, their values in octal, and the permission bit or bits to which each
one corresponds.
Table 2-2. Macros for permission bits and their octal values
Macro Octal value Permission bit(s)
S_IRWXU 0700 Owner read, write, execute
S_IRUSR 0400 Owner read
S_IWUSR 0200 Owner write
S_IXUSR 0100 Owner execute
S_IRWXG 0070 Group read, write, execute
S_IRGRP 0040 Group read
S_IWGRP 0020 Group write
S_IXGRP 0010 Group execute
S_IRWXO 0007 Other/world read, write, execute
S_IROTH 0004 Other/world read
S_IWOTH 0002 Other/world write
S_IXOTH 0001 Other/world execute
umasks are a useful tool for users, allowing them to limit the amount of access others
get to their files. Your program should make every attempt to honor the users’
wishes in this regard, but if extra security is required for files that your application
generates, you should always explicitly set this permission yourself.
See Also
Recipe 2.4
2.8 Locking Files
Problem
You want to lock files (or portions of them) to prevent two or more processes from
accessing them simultaneously.
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